A conventional 3D display is capable of displaying a pair of stereoscopic images in different directions so that an observer can see each image in his or her respective eye. To allow the observer to receive the pair of image components to form an autostereoscopic view, the images are displayed in directions symmetrical to each other such that the left and right eye can receive its respective image simultaneously and symmetrically. The notion of a dual-view display is similar to a 3D display in that it can too simultaneously display two images in different directions on a single display panel. In principle, a dual-view display is different from a 3D display in that the images of a dual-view display can be of unrelated contents so that observers viewing from different locations, such as a right or left viewing window of the display, can perceive different visual images. For instance, in the application of a motor car display, the driver may be restricted to view navigation information shown on the left viewing window of the car display while the passenger may view another image content such as a movie on the right viewing window. Typically, the right and left viewing windows of the display are symmetrical in terms of their angular extends with respect to the normal of the display.
FIG. 1 shows a schematic cross sectional view (not to scale) of a symmetrical dual-view LCD display device 1 based on a rear barrier 6 with opaque regions 14 being reflective on the side opposite to the backlight system 8. The dual-view LCD display device 1 comprises a display panel 2 including a color filter substrate 3 and a TFT liquid crystal substrate 5 with a pixellated color filter layer 4 interposed therebetween. The barrier 6 which lays upon a transparent barrier substrate 7 is provided on the rear side of the display panel 2 such that the backlight passes through transmissive regions 11 of the barrier 6 and then to the color filter layer 4. The front of the display panel and the rear end of the substrate may be further provided with a polarizer film 9. The barrier 6, in the embodiment shown, is applied at the rear side of the display panel 2 to generate dual views or a pair of autostereoscopic image components.
The display panel 2 includes the color filter layer 4 which comprises a plurality of pixels each having a number of sub-pixels. As shown in FIG. 1, a row of pixels having RGB sub-pixels (not to scale) is disclosed and each sub-pixel across the display panel, both in lateral rows or longitudinal columns, is assigned to either a primary right viewing window PR or a primary left viewing window PL. As shown in the figure, viewing window PR refers to the angular extend denoted by the dotted lines whereas the angular extend of viewing window PL is marked in solid lines. For ease of illustration, neither the unwanted secondary view SV indicated by thin solid lines nor the crosstalks will be further discussed in this paper. In the case of a 3D display, for example, the PR may coincide with the right-eye viewing window of an observer whereas PL may coincide with the left-eye viewing window such that an autostereoscopic view can be achieved. Likewise, for a dual-view display, the PR may refer to the right viewing window of an observer and the PL may be assigned to the left viewing window of another observer. The width of the views or the horizontal/vertical viewing angles of the display is limited by the thickness of the display panel 2, in particular the thickness of TFT liquid crystal substrate 5, which defines the distance between the barrier 6 and the pixellated color filter layer 4.
For the purpose of illustration, FIG. 2 shows a simplified schematic side view of a dual-display/3D display consisting of a color filter layer 4 with a plurality of sub-pixels and a barrier 6. The sub-pixels in a row of the pixel matrix are being alternatively assigned to either the PL or PR as R-1, G-2, B-1, R-2, G-1, B-2 etc, in which the symbols of -1 and -2 may refer to a left view sub-pixel associated with the PL and a right view sub-pixel associated with the PR, respectively. Taking G-2 and B-1 as examples, note that the areas or angular extends of G-2 and B-1 are symmetrical. This is typical for a dual-view/3D display wherein symmetrical views are displayed at substantially the same viewing angles with respect to the normal of the display panel. In other words, the angular extends of PL and PR are equal. As shown in the figure of a symmetrically aligned display, the left viewing window PL and its angular extend can be further defined by the angles L_max and L_min. Angle L_max refers to the angle between the imaginary normal 0 of the display and the maximum possible viewing angle of any one of the sub-pixels assigned to PL, for instance G-2 in this case, via the transmissive region 11 of the barrier 6. L_min is the minimum viewing angle of any of the sub-pixels assigned to PL with respect to the normal 0 via the barrier 6. Considering the images formed by the sub-pixels assigned to PL as a whole, the angular extend of PL is the angle between L_max and L_min. Similarly, PR can be indicated by angles R_min and R_max and the angular extend of PR is between R_max and R_min. Typically, the angles R_max and L_max are less than 90 degrees from the normal 0 due to the thickness of the display; and the angles are equal to each other to have symmetrical viewing windows PL and PR.
A dual view display having symmetrical views or viewing windows is not always suitable for all applications. For instance, in the case of a motor car dual display, having the driver's view zone being identical to that of the passenger's view zone may pose potential safety hazards because the driver can accidentally cross over the driver view zone or viewing window, which is no greater than that of the passenger's, to view the image content displayed in the passenger view zone. To prevent this from happening, a dual view display can be made to have asymmetrical viewing angles such that the view zones of the driver and the passenger are asymmetrical relative to each other.
One solution to the asymmetric dual view display is to provide a shift to the barrier with respect to the display panel such that the primary right viewing window PR and the primary left viewing window PL of the display are displaced such that the asymmetric viewing of PR and PL can be realized. FIG. 3 shows a simplified schematic side view of an asymmetric aligned dual-view display for which the asymmetry is realized by giving the barrier 6 a shift with respect to the (main) display comprising a pixellated color filter layer 4. By shifting the barrier 6 having transmissive regions 11 with a width W and a distance D relative to the sub-pixels (R-1, G-2, B-1, R-2, G-1, B-2 . . . ), the viewing window PL having angular extend between the angles of La_max and La_min can be made different from the viewing window PR with the angular extend defined by the angles of Ra_max and Ra_min. As shown in FIG. 3, angle La_max is greater than angle L_max (FIG. 2) and angle Ra_max is smaller than angle R_max (FIG. 2). Consequently, La_max is larger than Ra_max, meaning that the outer viewing angles are different for the primary right viewing window PR and the primary left viewing window PL. In other words, different angular extends of PL and PR may be obtained by the shift of the barrier; however, all the viewing angles associated with the PL and PR may too become asymmetrical including the tilted outer boundaries of the viewing windows. This is a drawback of an asymmetric aligned display realized by barrier shifting.